Pope Benedict XVI has praised the "great generosity" of American Catholics in welcoming new immigrants and backed the commitment of bishops in the United States to immigration reform.
Benedict on Friday held the last of a series of periodic meetings with American bishops over the past few months, saying the church must embrace "the rich patrimony of faith" from newly arrived Hispanic, Asian and African Catholics.
He acknowledged that immigration reform -- a hot button issue in the election campaign -- is a complex civil and political issue.
In his earlier meetings with the visiting U.S. bishops, Benedict has touched on other controversial issues that have featured in the presidential campaign, including condemning the gay marriage lobby and stressing the need for the Catholic Church to be free to pursue its religious teaching.
"I would begin by praising your unremitting efforts, in the best traditions of the church in America, to respond to the ongoing phenomenon of immigration in your country," the pope said.
"The Catholic community in the United States continues, with great generosity, to welcome waves of new immigrants, to provide them with pastoral care and charitable assistance, and to support ways of regularizing their situation, especially with regard to the unification of families.
A particular sign of this is the long-standing commitment of the American bishops to immigration reform," Benedict said.
"This is clearly a difficult and complex issue from the civil and political, as well as the social and economic, but above all from the human point of view. It is thus of profound concern to the church, since it involves ensuring the just treatment and the defense of the human dignity of immigrants," Benedict said.
In more general terms, Benedict spoke of the challenges facing the church, including threats to its unity.
He also singled out nuns for praise, saying, "I wish to reaffirm my deep gratitude for the example of fidelity and self-sacrifice given by many consecrated women in your country."
A recent Vatican demand for reform of the largest umbrella group for nuns in the United States has raised eyebrows and anger among some Catholics. The group, the Leadership Conference of Women Religious, is accused of taking positions that undermine Catholic teaching on the priesthood and homosexuality while promoting "certain radical feminist themes incompatible with the Catholic faith."